Sleep problems increase with age. The goal of this Program Project is to understand the nature of the changes in the underlying sleep regulatory processes in older people and the consequences on waking functions such as alertness and cognitive performance, as well as on metabolic functions that may result in age-related diabetes and cardiovascular disease. As part of this program, three related research projects are proposed that require quantitative assessment of sleep and wakefulness. Polysomnography (PSG) is the gold standard for such assessments. We have therefore developed a plan for the creation of a PSG Core in support of the three projects to ensure the accurate and efficient acquisition, analysis and interpretation of PSG derived measures of sleep and wakefulness. In recent years, PSG methodology has undergone dramatic changes that now allow for the collection and analysis of large digitized data sets. Moreover, these developments have resulted in a high degree of sophistication of PSG hardware and software that require a team of specialists who operate and maintain these tools. The general objective of the proposed PSG Core is to provide a knowledge base and an integrated infrastructure in support of three of the projects as well as the Analytic Core within the program. More specifically, the PSG Core will have the following objectives: 1. Acquisition and maintenance of PSG equipment and supplies; 2. Training of technical research staff in equipment use and instrumentation of research subjects for PSG; 3. Archival of digitized PSG data; 4. Vigilance state scoring of PSG recordings, and scoring of attention failures in wake recordings; 5. Quantitative analysis of the sleep and wake EEG with Fast Fourier Transform routine based spectral analysis in order to obtain measures of homeostatic sleep pressure and the circadian drive for sleep. Core C will enable and coordinate the utilization of shared facilities, equipment, and personnel. The Core will at the same time ensure standardized quality control criteria for the acquisition, analysis and interpretation of the data in all three projects. The data will be collected by trained PSG technicians of Core C, and GCRC technicians supervised by Core C staff. Core C will furthermore be responsible for the vigilance state scoring and quantification of the EEG with spectral analysis. This work will be carried out by a PSG technician of Core C, under close supervision of the Core Leader.